The first thing to do is goto My Documents folder and find your Maya version number in there. Hmm is it called documents & settings in english? Anyway, enter this folder and locate the prefs directory.
Backup this directory in a safe place so that you can restore it if the problem still persists.
Now, detele all the .mel files in the prefs directory, start Maya, and let maya create new default ones for you.
It will reset any gui problems. The drawback is you loose some of your hotkeys and marking menues, but those can be re-integrated.
If this didn't solve the problem, just put the backup you made back into the directory and nothing is lost.